Table 1. Characteristics of participants in UK Biobank by quintiles of circulating IGF-I concentrations (N = 438,453).
| Circulating IGF-I | |||||
|---|---|---|---|---|---|
| Fifth 1 | Fifth 2 | Fifth 3 | Fifth 4 | Fifth 5 | |
| Number of participants | 87,716 | 87,686 | 87,687 | 87,696 | 87,668 |
| IGF-I concentration, nmol/L | 13.9 (2.2) | 18.3 (0.9) | 21.3 (0.8) | 24.1 (0.9) | 29.5 (4.0) |
| IGF-I concentration at follow-up, nmol/L | 15.1 (3.6) | 18.5 (3.3) | 20.8 (3.4) | 23.0 (3.6) | 26.9 (5.0) |
| Sex—Male, N (%) | 32,843 (37.4%) | 38,985 (44.5%) | 42,241 (48.2%) | 44,267 (50.5%) | 43,563 (49.7%) |
| Age, years | 59.1 (7.1) | 57.6 (7.6) | 56.4 (7.9) | 55.2 (8.2) | 53.3 (8.4) |
| Body mass index, kg/m2 | 28.6 (5.7) | 27.5 (4.9) | 27.2 (4.5) | 27.0 (4.3) | 26.7 (4.1) |
| Height, cm | 166.3 (9.0) | 167.9 (9.1) | 168.9 (9.2) | 169.6 (9.3) | 170.0 (9.3) |
| Physical activity, N (%) | |||||
| Low | 27,983 (31.9%) | 25,238 (28.8%) | 24,743 (28.2%) | 24,279 (27.7%) | 24,268 (27.7%) |
| Moderate | 39,236 (44.7%) | 41,613 (47.5%) | 42,547 (48.5%) | 43,413 (49.5%) | 44,324 (50.6%) |
| High | 16,609 (18.9%) | 17,518 (20.0%) | 17,427 (19.9%) | 17,262 (19.7%) | 16,355 (18.7%) |
| Townsend deprivation index, N (%) | |||||
| Q1—Most affluent | 15,780 (18.0%) | 17,546 (20.0%) | 17,959 (20.5%) | 18,385 (21.0%) | 18,457 (21.1%) |
| Q5—Most deprived | 20,242 (23.1%) | 17,454 (19.9%) | 16,698 (19.0%) | 16,273 (18.6%) | 16,277 (18.6%) |
| Education, N (%) | |||||
| National examination at age 16 years | 15,029 (17.1%) | 14,887 (17.0%) | 14,650 (16.7%) | 14,445 (16.5%) | 14,337 (16.4%) |
| National examination at age 17–18 years | 4466 (5.1%) | 4671 (5.3%) | 4750 (5.4%) | 4909 (5.6%) | 5234 (6.0%) |
| College or University degree | 46,604 (53.1%) | 50,778 (57.9%) | 53,306 (60.8%) | 54,863 (62.6%) | 56,767 (64.8%) |
| Smoking, N (%) | |||||
| Never | 44,447 (50.7%) | 46,438 (53.0%) | 47,966 (54.7%) | 49,401 (56.3%) | 51,656 (58.9%) |
| Previous | 32,797 (37.4%) | 31,151 (35.5%) | 30,139 (34.4%) | 28,923 (33.0%) | 26,912 (30.7%) |
| Light smoker: < 15 cigarettes/day | 2835 (3.2%) | 2652 (3.0%) | 2638 (3.0%) | 2543 (2.9%) | 2687 (3.1%) |
| Medium smoker: 15–29 cigarettes/day | 3619 (4.1%) | 3353 (3.8%) | 3003 (3.4%) | 2910 (3.3%) | 2861 (3.3%) |
| Heavy smoker: ≥ 30 cigarettes/day | 3357 (3.8%) | 3563 (4.1%) | 3475 (4.0%) | 3496 (4.0%) | 3170 (3.6%) |
| Alcohol intake, N (%) | |||||
| < 1 g/day | 11,842 (13.6%) | 9684 (11.1%) | 8963 (10.3%) | 8921 (10.2%) | 9550 (11.0%) |
| 1–9.99 g/day | 25,849 (29.7%) | 26,400 (30.3%) | 27,061 (31.1%) | 27,666 (31.7%) | 30,219 (34.7%) |
| 10–19.99 g/day | 15,965 (18.4%) | 18,608 (21.4%) | 19,360 (22.2%) | 20,318 (23.3%) | 20,405 (23.4%) |
| ≥ 20 g/day | 23,845 (27.4%) | 25,549 (29.3%) | 25,420 (29.2%) | 24,301 (27.9%) | 20,830 (23.9%) |
| None drinkers | 9483 (10.9%) | 6885 (7.9%) | 6342 (7.3%) | 5983 (6.9%) | 6160 (7.1%) |
| Ethnicity, N (%) | |||||
| White | 82,375 (93.9%) | 82,788 (94.4%) | 82,794 (94.4%) | 82,664 (94.3%) | 82,060 (93.6%) |
| Mixed Race | 463 (0.5%) | 485 (0.6%) | 525 (0.6%) | 514 (0.6%) | 629 (0.7%) |
| Indian/Pakistani | 1952 (2.2%) | 1424 (1.6%) | 1336 (1.5%) | 1249 (1.4%) | 1124 (1.3%) |
| Chinese, Asian or other Asian | 502 (0.6%) | 556 (0.6%) | 559 (0.6%) | 669 (0.8%) | 750 (0.9%) |
| Black or Black British | 1202 (1.4%) | 1196 (1.4%) | 1284 (1.5%) | 1451 (1.7%) | 1818 (2.1%) |
| Other | 766 (0.9%) | 777 (0.9%) | 797 (0.9%) | 773 (0.9%) | 894 (1.0%) |
| Diabetes—Yes, N (%) | 7068 (8.1%) | 4227 (4.8%) | 3691 (4.2%) | 3431 (3.9%) | 3499 (4.0%) |
| Women-only covariates: | |||||
| Current HRT users, N (%) | 7014 (12.8%) | 3714 (7.6%) | 3060 (6.7%) | 2448 (5.6%) | 2144 (4.9%) |
| Current oral contraceptive pill users, N (%) | 370 (0.7%) | 522 (1.1%) | 685 (1.5%) | 947 (2.2%) | 1892 (4.3%) |
| Menopause status at recruitment, N (%) | |||||
| Premenopausal | 4426 (8.1%) | 6975 (14.3%) | 8945 (19.7%) | 11,533 (26.6%) | 16,420 (37.2%) |
| Postmenopausal | 46,494 (84.7%) | 37,441 (76.9%) | 32,244 (70.9%) | 27,605 (63.6%) | 23,251 (52.7%) |
Values are mean (SD) unless otherwise indicated, percentages include unknown category for missing data
Percentages calculated including missing values and therefore may not add up to 100%
g grams, HRT hormone replacement therapy, IGF-I insulin-like growth factor-I, N Number of participants, Q quintile, SD standard deviation